This invention relates to the construction of cabinets and housings to contain electronic equipment such as electronic computers.
It has been common to construct such cabinets from sheet metal formed to provide structural bracing or to use sheet metal panels secured to a metal frame. The interior of the cabinet has to be provided with fittings on which the electronic equipment is mounted. A hinged door is usually provided to protect the internal equipment from damage and to prevent accidental injury to personnel using the equipment. A gasket is often provided between the door and the cabinet both to provide an airtight seal so that cooling air does not have an egress between the door and the cabinet and to provide continuity in the screening against radio frequency interference. For this latter purpose the gasket is conductive. A latch mechanism ensures that the door and cabinet are drawn into engagement with the gasket interposed therebetween. Such constructions of cabinet are somewhat labour intensive and hence are costly to manufacture.
In order to reduce the cost of manufacture of cabinets, it has been proposed to construct the cabinets of mouldings of plastics material. The use of mouldings of plastics material permits a considerable simplification in the manufacturing process because a complex panel or other structural unit may be formed in a single moulding operation and the individual panels may be formed with integral means which interlock with adjacent panels thereby dispensing with the need for any structural framework. However, due to the inherent flexibility of moulded plastics panels it is necessary to provide interlocking means between panels at relatively closely spaced intervals. This is especially important when the cabinet is utilised to provide screening against radio frequency interference. Since the plastics material is electrically non-conductive, the inner surface of the panels is coated with a conductive layer. This may be accomplished by spray coating with conductive paint. In order to ensure that the conductive layer has no electrical discontinuities between adjoining panels, means are provided to electrically bond the conductive layers together. Where fixed panels adjoin one another it is relatively easy to ensure that they are mechanically interlocked to provide a relatively rigid assembly and to ensure the continuity of the inner conductive coating. However, in order to be able to maintain and service the equipment housed in the cabinet it is necessary to provide at least one panel which is easily removable. In metal cabinets it is common to provide a hinged door with a latch for this purpose because the door is relatively rigid and the rigidity of the cabinet does not depend upon interaction with the door.